1. Field of the Invention
The present invention relates to an engine control system and method, in particular, to those for stopping the idling operation of the engine based on specific conditions, and restarting the engine based on other specific conditions.
2. Description of the Related Art
Recently, environmental problems such as global warming have become the focus of attention, and electric cars and hybrid vehicles have been actively developed so as to reduce the discharge of carbon dioxide and the like. Electric cars have no exhaust gas discharge; thus, they are most preferable in consideration of the environmental problems. However, the possible driving distance per single charge is short; thus, it is necessary to examine the practical possibility of vehicles employing an engine.
On the other hand, hybrid vehicles comprise an engine and an (electric) motor, where the battery is charged using the rotation of the engine. When the discharge of carbon dioxide or the like is relatively large and the engine (rotation) speed is low, it is possible to drive the vehicle by only using the motor or by using both the engine and motor, thereby decreasing the discharge of carbon dioxide. Recently, the hybrid vehicles have found practical use because the discharge of the carbon dioxide can be reduced and long-distance driving is possible while the characteristics specific to conventional vehicles (i.e., driving distance, operability, and the like) can be maintained.
Under such circumstances, a technique for automatically stopping the engine (that is, the engine is stopped, but not by an operation by the driver) has recently become the focus of attention, where the objective of this technique is to reduce the discharge of carbon dioxide by combustion of the fuel or to reduce fuel consumption, by stopping the engine during idling (i.e., an xe2x80x9cidle stopxe2x80x9d control). However, it is undesirable to attach too much importance to reduction of exhaust gas discharge at a considerable sacrifice to the operability of the vehicle. In particular, hybrid vehicles can have a long cruising range as described above, and can be expected to find widespread use in the future. Therefore, it is necessary to ensure an operability similar to that realized by currently used vehicles while reducing exhaust gas discharge. In an example hybrid vehicle employing a CVT (continuously variable transmission), a plurality of driving modes (for driving the vehicle) are provided.
The driving mode used for ordinary driving is called the D range (i.e., drive mode). Generally, conventional vehicles also have an S range (i.e., sport mode) in which (i) the set torque at the vehicle start is higher in comparison with the D range, so as to obtain faster acceleration, and (ii) the CVT ratio is set higher at a high-speed driving mode. This sport mode provides a feel of xe2x80x9csportyxe2x80x9d driving.
In order to realize a comfortable driving operability, a hybrid car to be generally used should provide an S range as well as a D range, and in known hybrid vehicles, the range can be switched to the S range by an operation by the driver. This switching operation is conventionally carried out using a shift lever. However, in order to improve the operability for the driver, the provision of a set button in the vicinity of or on the steering wheel has been considered recently.
However, if the xe2x80x9cS rangexe2x80x9d driving mode is set by using the above set button while the engine is automatically stopped, the driver may experience a feeling of unease. For example, if the driver pushes the set button for choosing the S range while the vehicle is stopped, then the engine is restarted. In this case, the driver (who selects the S range) may want to select the sport mode for the next time he or she drives, or the driver may want to immediately drive in the sport mode.
In consideration of the above circumstances, an objective of the present invention is to provide an engine control system and method for reducing a feeling of unease felt by the driver relating to the operation of driving a vehicle which is idle-controlled so as to reduce the exhaust gas discharge, thereby improving the driving operability.
Therefore, the present invention provides an engine control system for automatically stopping/starting an engine according to conditions of use of a vehicle, the system comprising an engine start/stop control device and an automatic transmission, wherein:
the automatic transmission, having driving modes of a first normal driving range and a second normal driving range different from the first normal driving range, comprises:
a driving mode switch detecting section for detecting a switch of the driving mode from the first normal driving range to the second normal driving range;
an automatic stop detecting section for detecting whether the engine is currently in a stopped state due to an automatic stop operation; and
a brake state detecting section for detecting whether a brake for stopping the vehicle is currently being operated, and
the engine start/stop control device comprises:
a control section for automatically starting the engine if it is determined by the automatic stop detecting section that the engine is currently in a stopped state due to the automatic stop operation, and if it is determined by the driving mode switch detecting section that the driving mode has been switched to the second normal driving range, and if it is determined by the brake state detecting section that the brake is not currently being operated.
The present invention also provides an engine control method for automatically stopping/starting an engine according to conditions of a vehicle, comprising the steps of:
detecting a switch of the driving mode of the vehicle from a first normal driving range to a second normal driving range different from the first normal driving range;
detecting whether the engine is currently in a stopped state due to an automatic stop operation;
detecting whether a brake for stopping the vehicle is currently being operated; and
automatically starting the engine if it is determined that the engine is currently in a stopped state due to the automatic stop operation, and that the driving mode has been switched to the second normal driving range, and that the brake is not currently being operated.
In the above system and method, typically, the engine is automatically stopped during idling.
According to the present invention, while the engine is automatically stopped, if the driver switches the driving mode from the first normal driving range to the second normal driving range, then only if the brake is currently not being operated, the engine is restarted. Therefore, the engine is not restarted only as a result of the driver switching the driving mode, and the engine is restarted when the driver releases the brake pedal as in a normal driving operation. Accordingly, any feeling of unease which the driver may experience while driving is reduced, thereby improving the driving operability.